Know your coffee birds: Black-and-white Warbler

The Black-and-white Warbler (Mniotilta varia) is a small, zebra-striped bird that is unique among our warblers. It is the only representative of its genus, and also the only one whose typical mode of foraging is clinging to and climbing up and down tree limbs and trunks in search of prey found in bark crevices. Black-and-White Warblers breed across much of central and eastern Canada and the eastern U.S. in forested habitats. They winter in Florida and the Gulf Coast, the West Indies, southern Mexico, Central America, and northern South America.

On their tropical wintering grounds, Black-and-White Warblers are frequently found on shaded coffee farms. They were one of the most commonly encountered North American migrants in shade coffee farms of Chiapas, Mexico. In Venezuela, they were found foraging in the coffee understory as well as in the canopy of shade coffee farms. In Jamaica, Black-and-white Warblers were among the birds found on shade coffee farms that preyed upon coffee berry borers, a major coffee pest.

In the Dominican Republic, 65% of Black-and-White Warblers maintained winter residence on shade coffee farms, all of which were smaller than 9 ha. This site persistence indicates that there were adequate resources on these farms for the birds. An amazing 40% of warblers returned to the same farm in which they were originally captured and marked a year or more later. Most small songbirds, especially those that make twice-annual long-distance migrations, have very short lifespans, so this return rate is impressive. It also underscores that migratory birds rely on finding their winter habitats intact when they return from nesting in order to survive.

Since 1973, researchers have been monitoring overwintering migrant birds in Puerto Rico, where Black-and-white Warblers are one of the most common species. They have documented a distressing decline in this species, which now occurs at less than 20% of its original abundance. While the study does not take place on coffee farms, it supports North American Breeding Bird Survey data, which has documented a significant decline of around 1% annually for breeding populations over the same period.

Black-and-white Warblers are still one of the most familiar New World warblers. Yet the studies cited above, as well as others, indicate that even abundant and adaptable species like this one are vulnerable to habitat loss and alteration. Plenty of research has shown that shade coffee farms are important wintering habitat for Black-and-white Warblers. Let’s make sure that when they make their annual sojourn to the tropics, they continue to find these farms for their winter homes.

I had no idea that drinking coffee could be of so much help in helping our Songbirds. I am an avid lover of birds and also drink my share of coffee. Thanks for the information, you are doing a great job!